Two reactive materials are injected into a closed mold. They polymerize and set to final shape within the mold.
Two part thermoset polymers commonly used for the RIM process include dicyclopentadiene (DCPD) and polyurethane. Reinforcing materials can be added as well, but are not necessary to make high strength, impact resistant parts.
Two piece aluminum molds are typically used for the RIM process.
Most RIM parts accept paint very well and can be fabricated in the same manner as other composite materials.